Numerical Simulation And Optimization Of Internal Flow Field Inside A Pulse-Jet Bag Filter With Different Bag Length

With the air pollution becoming more and more seriously, it became the focus of attention about how to remove particles effectively. The bag filter was put forward higher requirements on its performance as a equipment that can handle industrial particles efficiently. At before some scholars studied the influence on bag filter about the different ways of entrance, the number of filter bag and the guide plate. This article mainly studied the optimization of pulse bag filters which had different bag length with the method of numerical simulation, the main contents are as follows:At first, the model came from an environmental protection company and the three dimensional flow fields in the bag filter with 6m, 8m and 10 m three different bag length were numerically simulated. The variation of speed and pressure distribution of flow field can be got according to the flow distribution coefficient, surface velocity distribution and filtration resistance. The results indicated that flow distribution coefficient Kqi closer to 1.0 in the case of 10 m. Under the same filtration velocity, the value of speed relative standard deviation was 6m>8m>10m. The velocity distribution was more uniform when the bag length was 10 m. Although the filtering resistance of the 10 m bag filter was higher, the advantage was obvious under the condition of low filtration velocity. Therefore, long bag filter was suitable for low filtration velocity.Secondly, it was numerical study of gas-solid two phase flow inside bag filters with three different bag lengths. The gas-solid two phase flow including different diameter particles in the bag filter with 6m, 8m and 10 m bag length were numerical simulated by simplified Eulerian model- Algebraic Slip Mixture Model(ASMM).The diameter of particles contained 1μm, 2.5μm, 5μm, 10μm and 20μm five types. Velocity contour, particle volume fraction and pressure drop of filters with different bag length were studied. The results showed that the internal flow field in bag filter became more uniform with the increase of filter bag’s length. The bag filter owned the ability to separate five kinds of particulates and the re-entrain dust had small influence on bag filter with 8m. When thickness of filter material and dust layer was 2mm, the pressure loss of filter bag augment ed with the increasing of the length, but in contrast, the influence of particle diameter was little. The reliability of the simulation result was verified by comparing simulation pressure drop and experimental results of filter with 8m bag length. In the all, 8m was the optimal length of bag filter.In the end, the pulse-jet process was simulated for a single filter bag of the pulse bag filter. The velocity of pulse blowing air inside the filter bag in the early period of increased rapidly and closed to the speed of sound. But with the end of the blowing, the air velocity decreased sharply. Analyzing the surface peak pressures about bag filters with 6m, 8m and 10 m three different bag length, we came to a conclusion that the longer the filter bag was, the smaller surface peak pressures would be. So filter bag length could not too long. As the injection pressure by 200 k Pa, 300 k Pa, 400 k Pa, 500 k Pa increased gradually, the surface peak pressure also increased gradually. But too much pressure value also easy to cause the breakage of the filter bag. In addition to the situation which the surface peak pressure value of injection time was 40 ms was significantly smaller, the curve of surface peak pressure when injection time was 60ms、100ms and 150 ms were similar. Under the condition of this study, the best condition for pulsing was that length of the filter bag was 8m and the injection pressure was 200 kpa with injection time for 100 ms.Through the study of this article about the comprehensive analysis of all kinds of stress nephogram, velocity contours, line charts and histograms, we concluded that this was the ideal performance of pulse bag filter when the length of the filter bag was 8 m under the condition of this study. The simulation results provided a significant theoretical basis for the improvement and optimization of bag filter.